Holey Optochip first to transfer one terabit of information per second

IBM scientists report on a prototype optical chipset, dubbed Holey Optochip,
that is the first parallel optical transceiver to transfer one trillion bits—one
terabit—of information per second, the equivalent of downloading 500 high-definition
movies.

With the ability to move information at high speeds—eight times faster than
parallel optical components available today—the breakthrough could transform
how data is accessed, shared and used for a new era of communications,
computing, and entertainment. The raw speed of one transceiver is equivalent to
the bandwidth consumed by 100,000 users at today's typical 10 Mb/s high-speed
internet access. Or, it would take just around an hour to transfer the entire
United States Library of Congress Web archive through the transceiver.

Progress in optical communications is being driven by an explosion of new
applications and services as the amount of data being created and transmitted
over corporate and consumer networks continues to grow. At one terabit per
second, IBM's latest advance in optical chip technology provides unprecedented
amounts of bandwidth that could one day ship loads of data such as posts to
social media sites, digital pictures and videos posted online, sensors used to
gather climate information, and transaction records of online purchases.

"Reaching the one trillion bit per second mark with the Holey Optochip marks
IBM's latest milestone to develop chip-scale transceivers that can handle the
volume of traffic in the era of big data," said IBM Researcher Clint Schow, part
of the team that built the prototype. "We have been actively pursuing higher
levels of integration, power efficiency, and performance for all the optical
components through packaging and circuit innovations. We aim to improve on the
technology for commercialization in the next decade with the collaboration of
manufacturing partners."

Optical networking offers the potential to significantly improve data
transfer rates by speeding the flow of data using light pulses, instead of
sending electrons over wires. Because of this, researchers have been looking
for ways to make use of optical signals within standard low-cost, high-volume
chip manufacturing techniques for widespread use.

Using a novel approach, scientists in IBM labs developed the Holey Optochip
by fabricating 48 holes through a standard silicon CMOS chip. The holes allow
optical access through the back of the chip to 24 receiver and 24 transmitter
channels to produce an ultra-compact, high-performing, and power-efficient
optical module capable of record setting data transfer rates.

The compactness and capacity of optical communication has become
indispensable in the design of large data-handling systems. With that in mind,
the Holey Optochip module is constructed with components that are commercially
available today, providing the possibility to manufacture at economies of
scale.

Photomicrograph of the back of the IBM Holey Optochip with lasers and photodectors visible through substrate holes. Image: IBM

Consistent with green computing initiatives, the Holey Optochip achieves
record speed at a power efficiency—the amount of power required to transmit a
bit of information—that is among the best ever reported. The transceiver
consumes less than five watts; the power consumed by a 100 W light bulb could
power 20 transceivers. This progress in power efficient interconnects is
necessary to allow companies who adopt high-performance computing to manage
their energy load while performing powerful applications such as analytics,
data modeling, and forecasting.

By demonstrating unparalleled levels of performance, the Holey Optochip
illustrates that high-speed, low-power interconnects are feasible in the near
term and optical is the only transmission medium that can stay ahead of the
accelerating global demand for broadband. The future of computing will rely heavily
on optical chip technology to facilitate the growth of big data and cloud
computing and the drive for next-generation data center applications.

Technical aspects of the Holey Optochip

Parallel optics is a fiber optic technology primarily targeted for high-data,
short-reach multimode fiber systems that are typically less than 150 m. Parallel
optics differs from traditional duplex fiber optic serial communication in that
data is simultaneously transmitted and received over multiple optical fibers.

A single 90-nm IBM CMOS transceiver IC with 24 receiver and 24 transmitter
circuits becomes a Holey Optochip with the fabrication of forty-eight
through-silicon holes, or "optical vias"—one for each transmitter and receiver
channel. Simple post-processing on completed CMOS wafers with all devices and
standard wiring levels results in an entire wafer populated with Holey
Optochips. The transceiver chip measures only 5.2 mm by 5.8 mm. Twenty-four
channel, industry-standard 850-nm VCSEL (vertical cavity surface emitting
laser) and photodiode arrays are directly flip-chip soldered to the Optochip.
This direct packaging produces high-performance, chip-scale optical engines.
The Holey Optochips are designed for direct coupling to a standard 48-channel
multimode fiber array through an efficient microlens optical system that can be
assembled with conventional high-volume packaging tools.